Before we talk about the support for the Theory of Evolution, we must briefly discuss the theory itself. In its most simplified form, the theory of evolution states that the make-up of organisms on earth have changed over time. While waiting to discuss the details of the causes of the change in chapter fifteen, the basic outline is as follows:

Variation exists among organisms

Some variations are better-suited to a new environment when the environment changes

Those organisms with variations that are not suited well enough to the new environment will die before being able to pass on their genes through reproduction and their variations will cease to exist

Those organisms with variations that are better-suited to the new environment will live to reproduce and their more "fit" variations will be passed on

When the environment chages again, these variations which have been most fit may become less well-suited to the environment

This theory, while as empirically sound as other well-accepted scientific theories, is quite controversial. Part of the controversy stems from the fact that the full process of "macro-evolution" has never been directly observed as it happens. We have indeed been able to observe one species evolving into another species, especially in organisms such as viruses and bacteria, but skeptics claim this is only "micro-evolution". What people really need is to see how a fish could evolve into something like a chimpanzee or a human. The time required for this type of change to occur is far beyond that of a human lifetime. In fact, it is far beyond that of the existence of all human beings, so it could never be observed directly. But it has been, and can be, observed indirectly. This chapter is about those observations which support the theory of evolution.

There are many pieces of evidence, from many different scientific disciplines, that come together to support the theory of evolution. The age of the earth, fossils, homologous structures, vestigial organs, developmental similarities, and molecular evidence (DNA, etc.) all contribute. To understand the evidence, the background presented before this chapter is required.